Conventionally, distillation has been mainly used as a method for separating water from water-containing mixture (dehydration). However, the separation method using the distillation needs high energy, and thus a separation method with low energy consumption has been proposed from the viewpoint of energy saving or the like.
For example, an organic membrane and an inorganic membrane are used as a separation membrane used in a dehydration method using membrane separation, but there is a case that they cannot be used depending on properties of mixed solution. For example, the organic membrane is poor in heat resistance and chemical resistance. A zeolite membrane or a silica membrane is used as the inorganic membrane, but A type zeolite membrane (e.g., see Non-Patent Document 1) among zeolite membranes is low in acid resistance and is not suitable for dehydration of acid solution. A T type zeolite membrane (e.g., see Non-Patent Document 2) or an MOR type zeolite membrane (e.g., see Non-Patent Document 3) is high in acid resistance as compared with the A type zeolite membrane, but the T type zeolite membrane does not have sufficient acid resistance yet. In contrast, the silica membrane (e.g., see Patent Document 1) is high in acid resistance, but new improvement of the silica membrane is desired from the viewpoint of separation performance.
Non-Patent Document 1: Development of Membrane Aided reactor, Mitsui Zosen Technical Review, February, 2003, No 178, 115-120
Non-Patent Document 2: Y. Cui et al., Zeolite T membrane: preparation, characterization, pervaporation of water/organic liquid mixtures and acid stability, Journal of Membrane Science, 2004, 236, 17-27
Non-Patent Document 3: L. Casado et al., Preparation, characterization and pervaporation performance of mordenite membranes, Journal of Membrane Science, 2003, 216, 135-147
Patent Document 1: Japanese Patent No. 2808479